An investigation of the major specific antigens of Mycobacterium tuberculosis, M. kansasii, M. intracellulare, and M. scrofulaceum is proposed. we will attempt to identify, characterize, and isolate species-specific mycobacterial antigens in form suitable for investigations of mycobacterial taxonomy and of the epidemiology and immunodiagnosis of tuberculosis and other mycobacterial infections. Using immunochemical techniques, species-specific mycobacterial antigens will be sought and characterized in unheated sterile culture filtrates. We will combine physiocochemical and immunoabsorbent affinity techniques to purify individual antigens and we will prepare monospecific antisera to these antigens. Each antigen will be characterized physicochemically, immunochemically, and immunobiologically. Its species distribution will be surveyed. Selected antigens will be hydrolyzed and attempts made to recover peptides containing specific antigenic determinants. We will evaluate immunofluorescent staining with specific antisera for the specific identification of mycobacteria.